package work.zhengyun.demo.nio;

import org.nustaq.kson.KsonCharOutput;

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;

/**
 * @Author: zhengyun
 * @Email: 574860631@qq.com
 * @Date: 2021/3/23 23:30
 */
public class NIOServer {
    public static void main(String[] args) throws Exception {
        //创建ServerSocketChannel -> ServerSocket
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        //得到一个Selecor对象
        Selector selector = Selector.open();
        //绑定一个端口6666，在服务器端监听
        serverSocketChannel.socket().bind(new InetSocketAddress(6666));
        //设置为非阻塞
        serverSocketChannel.configureBlocking(false);
        //把serverSocketChannel 注册到 selector 中，事件为OP_ACCEPT
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        //循环等待客户端连接
        while (true){
            if(selector.select(3000)==0){//没有事件发生
                System.out.println("服务器等待了3秒，无连接");
                continue;
            }
            //如果返回>0,就获取相关的selectionKey集合
            //1.如果返的>0,表示已经获取到关注的事件
            //2.selector.selectedKeys()返回关注事件的集合
            //通过selectionKeys 反向获取通道
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            //遍历Set<SelectionKey>, 使用迭代器遍历
            Iterator<SelectionKey> keyIterator = selectionKeys.iterator();
            while ((keyIterator.hasNext())){
                //获取到SelectionKey
                SelectionKey key = keyIterator.next();
                //根据key 对应的通道发生的事件做相应处理
                if(key.isAcceptable()){//如果是OP_ACCEPT,有新的客户端连接
                    //该客户端生成一个SocketChannel
                    SocketChannel socketChannel = serverSocketChannel.accept();
                    System.out.println("客户端连接成功 生成一个socketChannel"+socketChannel.hashCode());
                    //将socketChannel 设置为非阻塞
                    socketChannel.configureBlocking(false);
                    //将socketChannel 注册到selec，关注事件为OP_READ，同时给socketChannel关联一个buffer
                    socketChannel.register(selector,SelectionKey.OP_READ, ByteBuffer.allocate(1024));
                }
                if(key.isReadable()){//发生OP_READ
                    //通过key 反向获取对应channel
                    SocketChannel channel =(SocketChannel) key.channel();
                    //获取到该channel关联的buffer
                    ByteBuffer buffer =(ByteBuffer) key.attachment();
                    channel.read(buffer);
                    System.out.println("form 客户端 "+ new String(buffer.array()));
                }
                //手动从集合中移动当前的selectionKey,防止重复操作
                keyIterator.remove();
            }
        }
    }
}
